For an application standpoint, this is handled in the exact same manner as receiving a REFER request without a Replaces header. If an application wishes to process the REFER request it should use the dum->makeInviteSessionFromRefer API.

When you receive an INVITE request (via the onNewSession callback) you may wish to see if a Replace header is present, in order for this new INVITE session to "take over" an existing session. In order to accomplish this you can use a convience function on the DialogUsageManager called findInviteSession which takes a Replaces header as an argument.